Subsequent to the grafting of the saphenous vein into the coronary vascular bed (aortocoronary bypass), many histological changes occur in the vein. Although these histological observations suggest that biochemical and pharmacological changes in the vein can also occur, the exact nature of these changes and how they may effect the contractile and mechanical characteristics of the grafted vessel have not been determined. In addition, the stimuli responsible for the often observed histological changes are also unknown. The objectives of this proposal are to determine the biochemical and pharmacological changes that occur in the saphenous vein following grafting and to relate these to observed contractile and mechanical characteristics. Having identified these changes, experiments will be performed to determine the stimulus responsible for these changes. Saphenous veins will be grafted into the coronary and femoral arterial beds or returned in situ. The effect of the coronary graft on myocardial function will be assessed by the use of chronically implanted flow probes and muscle segment length crystals on the ascending aorta and heart, respectively. After various periods of time (up to 2 months) the graft will be removed and compared to the non-grafted contralateral saphenous with respect to histological appearance, in vitro mechanical characteristics (passive length-tension and dose-response curves) and biochemical characteristics (actomyosin, elastin, collagen and DNA contents, as well as enzymatic and adrenergic receptor characteristics of membrane fractions). By comparing the characteristics of the three types of grafts (coronary, femoral, venous) it will be possible to determine if the changes are due to graft location, arterial pressure or the trauma of surgery.